Guys, I think we cannot determine how this works from what we know here. Like most of you, maybe, I thought early on that the buoy was like a ball held in the water by the tether, and wanting always to rise to the surface. And wanting never to return to its lowest point in the cycle, which it must do in order to repeat the pumping action that produces the energy needed to create electricity. I thought that was the reason why the pressure tanks were needed; to reverse the action of the pump and bring the sphere or buoy back down to the lowest point in its cycle, in time to ride the lift provided by the next wave and therefore produce power. But, how inefficient would that be.
Later reading on the CWE site led me to understand that the buoy was partially, if not almost wholly filled with seawater. I now believe the quantity of water inside the buoy can be adjusted to suit the wave conditions, as they change. Submarines have this facility. It is required to allow them to maintain a steady cruising level below the ocean surface. In this balanced state the CETO buoy tends to act more like a submerged log, than a hollow vessel, tending to rock, or wash back and forth with the energy momentum of each passing wave, rather than just rising up and falling down with the vertical component of the wave passing by. In this state, when it is floating at the depth that CCE want it to float, given the conditions, it has reduced upwards lift due to its buoyancy. The closer to zero upwards lift the better I am guessing. This is desirable because the buoy then moves more in harmony with the wave than against the wave.
As better explained in the linked article below, the motion of the buoy will be like a molecule in the water, it will move in a circular fashion. Again, as the article explains, the lower the level the buoy is tethered at, the smaller the diameter of the cirle it traces out as a wave passes it. If the buoy can match the circular wave motion without assistance from the surge chamber, the function of the surge chamber is mainly to draw the ram of the pump back into its cylinder until it is at its low point, ready to capture the energy of the next passing wave. If everything is working to plan, the flexibility, or slack, in the tether will be taken up by the ram being drawn back into the cylinder faster than the wave is carrying the buoy back to the bottom of its cycle. I expect the operation of the surge chamber will be managed to ensure that just a little, or minimum amount of tension is maintained in order to avoid wasting effort, or energy in dragging the buoy back to its bottom of cycle point; ready to go again. Plus, you would not want a slack tether being suddenly snapped taught by an outgoing wave.
So, from all this, I conclude that the power of the buoy, be it CETO 5 or 6, is a function of the mass of water inside the buoy (plus the buoy's construction) that is being moved by the energy in the passing wave, against the resistance of the pump. There must be many variables in this as CCE will be wanting to keep the buoy in exactly the right position, much like a submariner must sail his vessel, at all times. Of course, they will have many computer algorithms for sailing the buoys when they are in operation, constantly adjusting things as they go, and for estimating the design output of each buoy, be it CETO 5 or 6.
But, if you think about all these variables, in operation, you begin to understand why CCE is quite pleased with the success of CETO 5, and with having operated it successfully for 12 months. We probably have no real appreciation of just what they have accomplished.
All this is just first principles stuff on my part, so feel free to correct me if I have said anything in error here. I could be way off the mark.
